Field of the Invention
The present invention relates to a device which vertically applies a load to a specimen.
Description of the Related Art
Devices which vertically apply a load to a specimen support the specimen by a universal joint, or support the specimen by a combination of a spherical seat and a spherical seat receiver, to eliminate the influence of a load eccentric to the vertical direction (e.g., Japanese Patent Application Laid-Open No. 2-203241 and Japanese Patent Application Laid-Open No. 6-160258).
As long as the specimen to which a load is to be applied shifts or deforms under a load only in the vertical direction, a reasonably accurate measurement result can be obtained if the specimen is supported by a universal joint, or a pin joint of a combination of a spherical seat and a spherical seat receiver.
However, in a case where the specimen shifts horizontally, a pin joint alone cannot allow accurate application of a vertical load as will be described below. Unless the specimen is restrained from shifting horizontally, the specimen can shift horizontally during a load test. For example, a horizontal shift can occur when a vertical load is applied to the specimen while the specimen is held in suspension.
As shown in FIG. 8A, a test device 100, which applies a vertical load FV to a specimen S, includes a hydraulic actuator 101, support members 103, 104 supporting the hydraulic actuator 101 respectively on an upper part and a lower part of the hydraulic actuator 101, and a load cell 105 interposed between the upper support member 103 and a piston rod 102 of the hydraulic actuator 101. The support members 103, 104 each include a pin joint part PJ. If the specimen S shifts in a horizontal direction H as shown in FIG. 8B while a vertical load is being applied by the test device 100, a horizontal load FH, in addition to the vertical load FV, occurs on the hydraulic actuator 101. Accordingly, a load combining the vertical load FV and the horizontal load FH occurs on the specimen S, so that it is not possible to accurately apply only the vertical load FV to the specimen S.
Therefore, an object of the present invention is to provide a load application device which, even if a specimen shifts horizontally, can accurately apply only the vertical load that is to be imposed on the specimen.
Another object of the present invention is to provide an aircraft load application method which uses such a load application device and can accurately apply only the vertical load that is to be imposed on the airframe of an aircraft.